Method for preventing operational and manufacturing imperfections in piezoelectric micro-actuators

ABSTRACT

A method of manufacturing an actuator includes applying at least one layer of electrically-conductive material and at least one layer of electrically-insulative material to an actuator block, and separating the actuator block into a plurality of actuators, each actuator having at least one actuator finger. The electrically-conductive material and the electrically-insulative material are applied one layer upon another in an alternating manner to the actuator block in at least one actuator finger location. The layer of insulative material is larger in area than the layer of conductive material such that an insulative layer, applied to the actuator block and sandwiching a conductive layer between the insulative layer and the actuator block, at least partially encloses and electrically isolates the electrically-conductive layer by covering the conductive material on at least three sides.

RELATED APPLICATION

This application is a Divisional of U.S. patent application Ser. No.10/282,999, now U.S. Pat. No. 7,065,845, filed on Oct. 28, 2002.

BACKGROUND INFORMATION

The present invention relates to magnetic hard disk drives. Morespecifically, the present invention relates to a system and method forpreventing piezoelectric micro-actuator manufacturing and operationalimperfections.

In the art today, different methods are utilized to improve recordingdensity of hard disk drives. FIG. 1 provides an illustration of atypical drive arm configured to read from and write to a magnetic harddisk. Typically, voice-coil motors (VCM) 102 are used for controlling ahard drive's arm 104 motion across a magnetic hard disk 106. Because ofthe inherent tolerance (dynamic play) that exists in the placement of arecording head 108 by a VCM 102 alone, micro-actuators 110 are now beingutilized to ‘fine-tune’ head 108 placement, as is described in U.S. Pat.No. 6,198,606. A VCM 102 is utilized for course adjustment and themicro-actuator then corrects the placement on a much smaller scale tocompensate for the VCM's 102 (with the arm 104) tolerance. This enablesa smaller recordable track width, increasing the ‘tracks per inch’ (TPI)value of the hard drive (increased drive density).

FIG. 2 provides an illustration of a micro-actuator as used in the art.Typically, a slider 202 (containing a read/write magnetic head; notshown) is utilized for maintaining a prescribed flying height above thedisk surface 106 (See FIG. 1). Micro-actuators may have flexible beams204 connecting a support device 206 to a slider containment unit 208enabling slider 202 motion independent of the drive arm 104 (See FIG.1). An electromagnetic assembly or an electromagnetic/ferromagneticassembly (not shown) may be utilized to provide minute adjustments inorientation/location of the slider/head 202 with respect to the arm 104(See FIG. 1).

Utilizing actuation means such as piezoelectrics (see FIG. 3), problemssuch as electrical sparking and particulate-enabled shortage can exist.It is therefore desirable to have a system for component treatment thatprevents the above-mentioned problems in addition to having otherbenefits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides an illustration of a drive arm configured to read fromand write to a magnetic hard disk as used in the art.

FIG. 2 provides an illustration of a micro-actuator as used in the art.

FIG. 3 provides an illustration of a ‘U’-shaped micro-actuator utilizingmulti-layered piezoelectric transducers (PZT) to provide slideractuation.

FIG. 4 illustrates a potential problem of particulate-enabled shortingbetween piezoelectric layers.

FIG. 5 illustrates various problems affecting PZT performance.

FIG. 6 provides a cross-section of the micro-actuator arms with themicro-actuators unseparated and a cross-section of a micro-actuator armafter micro-actuator separation.

FIG. 7 provides a cross-section of the micro-actuator arms with themicro-actuators unseparated and a cross-section of a micro-actuator armafter micro-actuator separation under principles of the presentinvention.

FIGS. 8 a–b provide a cross-section of the micro-actuator arms with themicro-actuators unseparated and a cross-section of a micro-actuator armafter micro-actuator separation and ending with PZT layer applicationunder principles of the present invention.

FIG. 9 provides a cross-section of a finger of a micro-actuator underprinciples of the present invention.

DETAILED DESCRIPTION

FIG. 3 provides an illustration of a ‘U’-shaped micro-actuator utilizingmulti-layered piezoelectric transducers (PZT) to provide slideractuation. A slider (not shown) is attached between two arms 302,304 ofthe micro-actuator 301 at two connection points 306,308. Layers 310 ofPZT material, such as a piezoelectric ceramic material like leadzirconate titanate, are bonded to the outside of each arm (actuatorfinger) 302,304. PZT material has an anisotropic structure whereby thecharge separation between the positive and negative ions provides forelectric dipole behavior. When a potential is applied across a poledpiezoelectric material, Weiss domains increase their alignmentproportional to the voltage, resulting in structural deformation (i.e.regional expansion/contraction) of the PZT material. As the PZTstructures 310 bend (in unison), the arms 302,304 (which are bonded tothe PZT structures 310), bend also, causing the slider (not shown) toadjust its position in relation to the micro-actuator 301 (for magnetichead fine adjustments).

FIG. 4 demonstrates a potential problem of particulate-enabled shortingbetween piezoelectric layers. During manufacture and/or drive operation,particles may be deposited, and particle(s) 404 may end up bridgingconductive layers 406. Relative humidity can cause the particle(s) toabsorb moisture from the air, enabling electrical conduction between PZTlayers. This short 404 in the piezoelectric structure 406 can preventits normal operation, adversely affecting micro-actuator 402performance.

FIG. 5 illustrates various problems affecting PZT performance. FIG. 5 aprovides an image of a stray particle 504 bridging (and potentiallyshorting) piezoelectric layers 502. As stated above, humidity can causethe particle 504 to absorb moisture and become electrically conductive.FIG. 5 b provides an image of damage caused by electrical arcing 506between piezoelectric layers 508. Under the right conditions of voltageand air humidity, electricity may arc between piezoelectric layers 508,causing damage and deformation 506. FIG. 5 c provides an image of‘smearing’ 510 (and potentially shorting) between layers 512. Smearingcan occur during manufacture when the micro-actuators are cut forseparation. (See FIGS. 6 and 7). Material of the different layers 512 issmeared across one another as the cutting tool passes over the surfaceexposed by cutting.

FIG. 6 provides a cross-section of the micro-actuator arms with themicro-actuators unseparated and a cross-section of a micro-actuator armafter micro-actuator separation. FIG. 6 a illustrates a cross-section604 of a portion 602 of a micro-actuator block structure. Thecross-section 604 illustrates alternating layers 628 of conductivematerial 622 and PZT (insulating) material 624 applied to themicro-actuator. FIG. 6 b illustrates a cross-section 608 of amicro-actuator arm 606 after separating the micro-actuator 610 fromothers. Separation may be performed in one embodiment by mechanicalmeans (e.g., a rotating wheel blade or a straight edge knife). Otherembodiments involve electrical means for micro-actuator separation(e.g., electric sputtering or ion milling). Further, chemical means maybe used (e.g., chemical vapor deposition (CVD)). Note that the sides ofthe micro-actuator arm (finger) 606 expose the piezoelectric layers,including the electrically-conductive layers 622.

FIG. 7 provides a cross-section of the micro-actuator arms with themicro-actuators unseparated and a cross-section of a micro-actuator armafter micro-actuator separation and ending with conductive layerapplication under principles of the present invention. FIG. 7 aillustrates a cross-section 704 of a portion 702 of a micro-actuatorblock structure. FIG. 7 b illustrates a cross-section 708 of amicro-actuator arm 706 after separating the micro-actuator 710 fromothers. In one embodiment of the present invention, after a set ofconductive strips (conductive material) 712, such as gold, platinum orcopper, are placed upon the micro-actuator arm 706, a PZT layer(insulative layer) 714 is applied over and between the conductive strips712, physically and electrically isolating the conductive strips 712.Another set of conductive strips 712 and a PZT layer 714 are applied andthe process is repeated until the number of layers and/or thickness isappropriate for the micro-actuator's application and performance. In oneembodiment, the last layer applied is the conductive strip 712, followedby the placement of a bonding pad 716 upon the piezoelectric layers (andon opposite ends 717 of the micro-actuator finger 706, see also FIG. 9).In one embodiment, four to six layers PZT layers are utilized (five toseven conductive layers).

In one embodiment, upon separation of the micro-actuators 710, the PZTlayers 714 physically isolate the conductive strips 712 from each other,and thus, prevent ‘smearing’ (and potential shorting). Further, the PZTlayers 714 electrically insulate the sides of the piezoelectric layers,preventing ‘arcing’ damage and particulate contamination (electricalbridging/shorting).

FIG. 8 provides a cross-section of the micro-actuator arms with themicro-actuators unseparated and a cross-section of a micro-actuator armafter micro-actuator separation and ending with PZT layer applicationunder principles of the present invention. FIG. 8 a illustrates across-section 804 of a portion 802 of a micro-actuator block structure.FIG. 8 b illustrates a cross-section 808 of a micro-actuator arm 806after separating the micro-actuator 810 from others. In one embodimentof the present invention, after a set of conductive strips (conductivematerial) 812, such as gold, platinum or copper, are placed upon themicro-actuator arm 806, a PZT layer (insulative layer) 814 is appliedover and between the conductive strips 812, physically and electricallyisolating the conductive strips 812. Another set of conductive strips812 and a PZT layer 814 are applied and the process is repeated untilthe number of layers and/or thickness is appropriate for themicro-actuator's application and performance. In one embodiment, thelast layer applied is a PZT layer 815. In one embodiment, the last PZTlayer 815 provides a ‘window’ (gap in insulation) for the bonding pad816 to be attached within. (See FIG. 8). In one embodiment, four to sixPZT layers and four to six conductive layers are utilized.

In one embodiment, upon separation of the micro-actuators 810, the PZTlayers 814,815 physically isolate the conductive strips 812 from eachother, and thus, prevent ‘smearing’ (and potential shorting). Further,the PZT layers 814,815 electrically insulate the sides of thepiezoelectric layers, preventing ‘arcing’ damage and particulatecontamination (electrical bridging/shorting).

FIG. 9 provides a cross-section of a finger of a micro-actuator underprinciples of the present invention. In an embodiment, a window 902 isprovided in the last PZT layer of 915 to give a conduction path betweenthe top conductive layer (strip) 904 and the bonding pad 906.

Although several embodiments are specifically illustrated and describedherein, it will be appreciated that modifications and variations of thepresent invention are covered by the above teachings and within thepurview of the appended claims without departing from the spirit andintended scope of the invention.

1. A method of manufacturing an actuator comprising: applying at leastone layer of electrically-conductive material and at least one layer ofelectrically-insulative material to an actuator block, wherein saidelectrically-conductive material and said electrically-insulativematerial are applied one layer upon another in an alternating manner tothe actuator block in at least one actuator finger location; and saidlayer of electrically-insulative material is larger in area that saidlayer of electrically-conductive material such that an insulative layer,applied to said actuator block and sandwiching a conductive layerbetween said insulative layer and said actuator block, at leastpartially encloses and electrically isolates said conductive layer bycovering said electrically-conductive material on at least three sides;and separating said actuator block into a plurality of actuators, eachactuator having at least one finger that extends from a portion of theactuator block.
 2. The method of claim 1, wherein separating isperformed by a cutting tool from the group consisting of a wheel blade,a straight edge knife, electric sputtering, ion milling, and chemicalvapor deposition.
 3. The method of claim 2, wherein said conductivematerial is from the group consisting of Gold, Platinum, and Copper. 4.The method of claim 1, wherein said conductive material is a metal. 5.The method of claim 1, wherein said insulative material is apiezoelectric ceramic material.
 6. The method of claim 5, wherein saidinsulative material is lead zirconate titanate.
 7. The method of claim1, wherein said actuator finger is a hard disk drive micro-actuatorfinger.